Ha, easy question. My top three are easily Kosak X Sylvanas, Metzen X Thrall and Afrasiabi X A Pissed Jaina.
I saw proposition about Baine x Mayla Highmountain. Which I think would be interesting if done right. But It should be done in longer span, with Baine getting some sharper edge. They also have things in common, and it would somehow unite two tauren tribes, oosting Horde numbers.
Vol'Jin x Khal'ak ,the Zandalari general - she was very into him. And tbh I would hope for Zandalari and Darkspears to join forces, as previously they had a very good relations. Too bad that MoP circumstanses were very unfortunate.
But all in all, WoW romances are quite obsolete and I was more moved by small NPCs romance, than I did for major heroes like that bloody love triangle between Tyrande and two Stormrage bros, Thrall x Aggra, and now even Khadgar gets World Quest for his crush.
How cute.
Meanwhile Horde runs around like headless chickens, no character developmen for their champions except Sylvanas' boyfriend :/
I miss Mists of Pandaria
Ragnaros x Neptulon.
Now THAT would be one steamy romance.
Garrosh did nothing wrong.
#MakeTheHordeGreatAgain
Anduin & Wrathion, of course. Because who's to say what's "normal" in a fantasy video game? We've already seen Jaina & Kalec.
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I would suggest Illidan & Maiev, but that one's already happening.
"I Am Vengeance. I Am The Night. I Am Felfáádaern!"
Valeera x Anduin
Illidan x Maiev
Khadgar x Modera
Bonus:
Yrel x Gorehowl
Mudmug x Pepe